In typical picture-taking scenarios, flash (or strobe) illumination is used for photographing relatively near subjects. A typical flash picture composition might comprise, for example, an indoor portrait. In contrast, non-flash scenarios might comprise subjects positioned at any distance from close up to infinity (i.e. a landscape).
In recognition of these generalities, it is known in the art to decrease the focus distance of a camera picture taking lens when a flash is enabled. U.S. Pat. Nos. 3,589,031 to Harvey (assigned to the assignee of the present invention) and 3,643,577 to Monachesi show cameras which operate thusly. In the Harvey patent, a fixed focus lens is provided for non-flash operations. When a flash is enabled, an auxiliary lens is positioned coaxially with the fixed focus lens to shorten the focus distance of the latter. The Monachesi patent shows a camera wherein the lens is focused by translation along the optical axis. In non flash operation, the lens is fixed to a relatively distant focus setting. When a flash is activated, the focus distance of the lens is shifted to a relatively closer focus setting. Both cameras, however, show somewhat dated technology, neither showing or suggesting the autofocus features popular with current consumers.
Japanese Kokai No. 59-204012 shows an autofocus camera including an adjustable focus lens and a strobe. A focusing mechanism is provided, including two separate ratchets and a pawl. Each of the ratchets includes a plurality of teeth, and each of the teeth define a focus setting for the lens. The teeth on the first of the ratchets are positioned for optimum focusing of the lens in the flash mode of operation, while the teeth on the second ratchet are positioned to provide optimum focusing of the lens in the non-flash mode of operation. A mechanism is provided for aligning the appropriate one of the ratchets with the pawl.
While the camera of Japanese Kokai No. 59-204012 functions to provide optimum focusing in both the flash and non flash modes of operation, it suffers from the disadvantages of complexity and costliness inherent in the use of the intricate focusing mechanism. More specifically, the use of multiple ratchets and a ratchet positioning relay add substantial expense and difficulty to the construction of such a camera.
Published Japanese Kokai No. 61-203429 shows an autofocus camera including a rangefinder for indicating the distance to a subject as one of two zones. The focus distance of the taking lens is set to one of two distances, depending on the indicated zone. When a built-in flash is activated, the change-over distance between the two zones is decreased. Concomittantly, the two focus settings for the lens are decreased. Thus, in the flash mode of operation, the autofocus camera functions to provide better focus at relatively closer distances.
The autofocus camera shown in Japanese Kokai No. 61-203429 suffers from the disadvantage of the inherent complexity of the mechanism shown for changing the focus settings of the lens. This mechanism requires two separate ratchet areas on a lens ring, two separate pawls, and two separate electro magnets for controlling the pawls. This `doubling` of focus apparatus increases the complexity and cost of the autofocus camera.
Japanese Kokai No. 59-202416 shows an autofocus camera including a fixed focus lens and an auxiliary telephoto lens which can be pivoted onto the optical axis. As shown in FIGS. 6-8 of this Kokai, a mechanism including a pawl and ratchet wheel is provided for focusing the telephoto lens at one of two focus distances, these distances being different in the flash mode of operation in comparison to the non flash mode of operation. As shown in FIG. 6, the ratchet wheel includes 3 consecutive teeth, each defining a discrete focus distance. In the non flash mode of operation, the focus setting for the lens is selected from between the first (one of the middle distance settings) and third (most distant) ratchet teeth. In the flash mode of operation, the focus setting for the lens is selected from between the `cocked` lens position (before the first ratchet tooth--the closest distance setting), and the second ratchet tooth (one of the middle distance settings). Thus, a single ratchet and pawl are used to provide two lens focus settings in both the flash and non-flash mode of operation.
Japanese Kokai No. 59-202416 suffers from the disadvantage of being limited in distance settings. More specifically, because the focus settings used in the flash and non-flash modes of operation are mutually exclusive, to provide more focus settings in each mode would require an inordinate number of ratchet teeth. Thus, the apparatus described in this Kokai is inherently limited in the number of focus settings available.
Japanese Kokai No. 59-202437 shows a single lens autofocus camera, including a single ratchet and pawl mechanism for selecting focus distance settings in a manner for selecting focus distance settings in a manner functionally equivalent to that described above with respect to Kokai No. 59-202416. While the former Kokai uses a single lens and a slightly different mechanical mechanism to effect focusing, it suffers from the same disadvantages inherent in the use of mutually exclusive focus settings for the flash and non-flash modes of operation.